1. Field of the Invention
The present invention relates to a microwave oven, and in particular to a heater system for a microwave oven which is capable of transferring heat from a heater to cooking object more efficiently.
2. Description of the Related Art
A microwave oven heats cooking object by using microwave energy. Recently, in order to add various heating functions to a microwave oven, a heater is installed as another heating source besides microwave energy and heat generated by the heater is used for heating cooking object.
FIG. 1 is a sectional view illustrating construction of a heater system for a microwave oven in accordance with a prior art.
As depicted in FIG. 1, in the heater system for the microwave oven in accordance with the prior art, a cooking chamber 2 is formed inside a cavity in order to cook cooking object F placed on a tray 2xe2x80x2.
An additional heater chamber 5 is formed at the upper portion of an upper plate 3 forming a ceiling of the cooking chamber 2, and heaters 7, 7xe2x80x2 for heating the cooking object F on the tray 2xe2x80x2 are installed inside the heater chamber 5.
And, a circulation fan 9 is installed at the center portion of the heater chamber 5, and is rotated by a circulation motor 10 on the upper portion of the heater chamber 5.
And, a suction portion 3S and a discharge portion 3E for air circulation generated by the circulation fan 9 are respectively formed on the upper plate 3 corresponded to the bottom surface of the heater chamber 5.
Herein, the suction potion 3S is formed at a position corresponded to the circulation fan 9, and the discharge portion 3E is formed at a position corresponded to the heaters 7, 7xe2x80x2. The suction portion 3S and the discharge portion 3E are formed as a plurality of air passage holes.
In the heater system for the microwave oven in accordance with the prior art, in order to perform heating with the heaters 7, 7xe2x80x2, power is applied to the heaters 7, 7xe2x80x2, heat is generated, and at the same time the circulation fan 9 is operated.
By the rotation of the circulation fan 9, air inside the cooking chamber 2 is sucked into the heater chamber 5 through the suction portion 3S, the sucked air is heated while passing through the heaters 7, 7xe2x80x2 in the heater chamber 5 and is discharged into the cooking chamber 2 through the discharge portion 3E.
The heated air discharged into the cooking chamber 3 heats the cooking object F and is again sucked into the heater chamber 5 through the suction portion 3S.
However, there are problems, which will be described in the following, in the heater system for the microwave oven in accordance with the prior art.
First, air flow inside the cooking chamber 2 is formed at the suction portion 3S at a center of the upper plate and the discharge portion 3E at the circumference on the basis of the ceiling of the cooking chamber 2 formed by the upper plate 3, and such air flow does not circulate the whole cooking chamber 2 uniformly.
In more detail, air flow is well-performed mostly at the upper center portion of the cooking chamber 2 adjacent to the circulation fan 9, air flow is not well-performed at the lower portion of the cooking chamber 2, especially at the corner portion of the cooking chamber 2, and accordingly air discharged through the discharge portion 3E is directly sucked into the suction portion 3S as shown with arrows in FIG. 1.
Accordingly, heat transfer inside the cooking chamber 2 is not uniform and the uniform heating of the cooking object F can not be performed.
In addition, air flowing into the heater chamber 5 by the circulation fan 9 is heated by passing through the heaters 7, 7xe2x80x2, passes the discharge portion 3E formed at the upper plate 3 and is discharged into the cooking chamber 2, herein lots of heat loss is occurred by transferring large amount of heat to the upper plate 3. In more detail, heat to be transferred to the cooking object F is transferred to the upper plate 3 first, accordingly heat loss occurs.
In the meantime, the air convection by the circulation fan 9 is performed by connecting the cooking chamber 2 and the heater chamber 5, for the convection of air, the discharge portion 3E is formed at the upper plate 3 corresponded to the heaters 7, 7xe2x80x2. However, impurities such as pieces of cooking object or fat, etc. in the cooking object 2 can be conveyed to the heaters 7, 7xe2x80x2 through the discharge portion 3E. Particularly, because the impurities in the cooking chamber 2 can spit to the upper portion of the cooking chamber 2, the heaters 7, 7xe2x80x2 can be easily contaminated.
Accordingly, in order to solve the above-mentioned problems, it is an object of the present invention to provide a heater system for a microwave oven which is capable of heating cooking object uniformly by improving convection of heat generated by heater.
It is another object of the present invention to provide a heater system for a microwave oven which is capable of transferring heat generated by heater to cooking object more efficiently.
It is yet another object of the present invention to provide a heater system for a microwave oven which is capable of improving operation reliability of a heater mostly using a radiation heat.
In order to achieve the above-mentioned objects, a heater system for a microwave oven in accordance with the present invention includes a cooking chamber having an upper surface and side walls; an air tunnel having a suction portion and a discharge portion, said air tunnel formed at the upper surface of the cooking chamber; a fan assembly installed inside the air tunnel, said fan assembly having a circulation fan forming air flow by sucking air inside the cooking chamber through the suction portion and discharging the sucked air through the discharge portion by passing the air tunnel; a first heater chamber having a first heater installed inside the air tunnel and heating air discharged through the discharge portion; and a second heater chamber having a second heater installed inside the air tunnel and emitting radiation heat into the cooking chamber, wherein the suction portion and the discharge portion are formed near opposite side walls of the cooking chamber.
In addition, the first heater chamber is installed directly at an upper portion of the discharge portion, is divided from the air tunnel by a first reflection plate having a plurality of connection holes, and is opened so as to be directly connected to the cooking chamber.
The second heater chamber is positioned between the suction portion and the discharge portion and is defined formed by a second reflecting plate. And it is preferable to install the second heater chamber between the suction portion and the discharge portion.
The second heater chamber is divided from the cooking chamber by a filter capable of permeating a radiation heat into the cooking chamber.
In the heater system for the microwave oven in accordance with the present invention, the air flow inside the cooking chamber by the circulation fan can be formed more uniformly, accordingly the heat can be transferred to cooking object more efficiently.